1. Field
The invention relates generally to a musical keyboard apparatus for controlling electronic sound, and specifically to those keyboards whose keys may be actuated both up-and-down and in-and-out.
2. Defined Terms
Positions and movements of keyboard elements are described from the point-of-view of a player facing the instrument.
The axis in which the plurality of keys is arrayed left and right is termed the x-axis, and motion in that axis is termed lateral, or side-to-side; the axis is which the long axes of the keys lie towards and away from the player is termed the y-axis, and motion in that axis is termed longitudinal, or in-and-out; and the axis in which the keys move up-and-down is termed the z-axis, and motion in that axis is termed vertical, or up-and-down.
Key movement in the z-axis is termed ‘depression’, or ‘key dip’, and key movement in the y-axis is termed ‘displacement’.
A key is said to be in its ‘at-rest’ position when it is fully up in the z-axis, or undepressed, and centrally located in the y-axis, or undisplaced; and in an ‘active position’ when it is not at-rest.
The term ‘unguided’ refers to the state of a key that has been depressed, whether or not displaced, and released.
The term ‘key space’ refers to the locus of all positions in the vertical plane in which the long axis of a key lies to which the key may be moved.
Of the two key forms, ‘upper-rank’ keys are analogous to those commonly called ‘black keys’ in conventional claviers, and lower-rank' keys are analogous to those commonly called ‘white keys’ in conventional claviers.
3. Prior Art
Tone producing means and control means in acoustic instruments are tightly bound to each other. A drumhead, for example, may be struck by hand, or with a stick—a distinction with a difference—but not so much you wouldn't know it was a drum.
Control means for electronic sound, on the other hand, may be entirely separate from tone producing means. Drum sounds can be played via keyboards, though, as is well understood by those skilled in the art, without the control of actually drumming.
Almost a century of effort since the Telharmonium (U.S. Pat. No. 580,035 (1897), Cahill) first made the sounds of electrical circuits audible has gone toward devising control means as expressive as those of acoustic instruments. The Telharmonium utilized multiple keyboards having position sensitivity in the z-axis to expand expression, but the instrument weighed several hundred tons and cost millions of dollars to fabricate.
Less inherently expensive but still very limited was the keyboard of Maurice Martenot (U.S. Pat. No. 2,562,471 (1948), Martenot). This patent teaches a platform, displaceable in the x or y-axis direction, on which all keys are mounted. The platform's excursion is directed at effects that can be controlled with short motion, like vibrato, but is not useful for control of higher resolution sonic events like pitch bending. Further, Martenot recognizes that the platform, when unguided, will continue to oscillate as a function of its mass and springing, eventually losing energy. Such oscillation is inherently distracting to the player, all the more so if it has a hearable result. Martenot's solution, balancing mass and spring force so that the platform has a natural frequency higher than that of an effect like vibrato, attempts to hide the problem of damping, and can only work for low frequency sonic events.
One known way to expand the expressive capability of an electronic keyboard controller is to recognize individual key-based playing gestures made in the direction of the longitudinal axis of the keys, in-and-out, in the y-axis.
Robert Moog described at the International Computer Music Conference in 1982 a ‘multiple-touch-sensitive keyboard’, later completed with help from one of us (DeRocco). The key surfaces of its otherwise conventional organ/synthesizer style keyboard were circuit boards that continuously recognized finger location. In one of its playing modes, absolute location of the initial contact in the y-axis was treated as a starting point for modulation, and in another, location relative to a ‘first touch’, that is, a note-on condition following a note-off condition, was recognized. Whichever the mode, however, player perception and control was principally mediated through skin sensation rather than via the more discriminating flexors and extensors of the hand.
The same ergonomic limitation applies to the more contemporary instrument taught in U.S. Pat. No. 6,703,552 (2004), Haken. The instrument is an uninterrupted planar surface (a membrane keyboard) with very sophisticated processing to extract player intent; but it, too, like Moog's keyboard, does not use the hand's more complex sensing and control capabilities.
FIG. 1a is a side elevational view of the prior art of U.S. Pat. No. 3,818,114 (1974), Okamoto, showing a digitally operable electronic organ key with limited 3-dimensional capability. A key 110 is supported by a leaf spring 111 “resilient enough to permit each . . . [key] . . . to move back and forth in the lengthwise direction of each said key”. Such motion is limited by interference between the ‘white’ key (as shown in the drawing) and a ‘black’ key (not shown). At the front end of the key, a member 112 supports a stop 113 at its upper end, which stop is “somewhat loosely received in a housing of any suitable shape formed on the underside of the key 110, in such a manner that the angle of swing of the key 110 is thereby delimited.” That is, the stop is only directed at and suitable for z-axis motion. Thus Okamoto shows a digitally operable electronic organ key with limited 3-dimensional capability. Its longitudinal, or y-axis, motion is very short, of necessity, as there is little space between the front of black keys and ‘L-shaped’ portions of adjacent white keys. Short key travel is suitable only for sonically low resolution musical features, like tremolo. Significantly greater travel in the y-axis would be needed to control higher resolution sonic events, like pitch. Also, Okamoto makes no provision for frictionless guidance at the front of the key; increased friction under the natural lateral loads in playing, having no sonic purpose, only distract the player. Okamoto speaks specifically of the restraint at the front of the key as “somewhat loosely received in a housing of any suitable shape formed on the underside of the key, in such a manner that the angle of swing of the key is thereby delimited.” The structure is directed only at z-axis motion and does not adequately support y-axis motion suited to control high resolution musical events. Finally, Okamoto makes no provision for physically signaling a key's center position in the y-axis.
FIG. 1b is a side elevation, partly sectionalized, view of the prior art of U.S. Pat. No. 4,068,552 (1978), Allen, showing an electronic key mechanism with extended 3-dimensional capability. The pin 115, which makes sliding contact with the inside of slot 116, is subject to binding if torsion is exerted on the key 114 through lateral loading, which is a natural component of playing. At the rear of the key, a pivoting mount is comprised of a yoke 117 to which the key 114 is pivotally pinned. The yoke 117 is then attached to a leaf spring 118. These joints are is a source of instability and play in the mechanism, require a complexity of parts, and the need for adjustment. While Allen describes an electronic key mechanism with extended key displacement range through the use of cantilevered, or undercut, ‘black keys’, the pin mechanism used to control lateral loads is susceptible to cocking and binding in its associated slot; no means is provided for damping the longitudinal oscillations of an unguided key; and the rear key mount requires a bearing in its upper aspect, at the expense of play which may be amplified over the length of the key, and shows a complexity of parts needing assembly and adjustment, and hampering long term reliability.
FIG. 1c is an exploded view of the prior art of U.S. Pat. No. 4,498,365 (1985), Tripp et al., showing a pressure and longitudinal sensor coupled to a longitudinally displaceable key with extended 3-dimensional capability and center signaling. A rocker assembly 119 establishes a central detent for longitudinal key motion through a complexity of elements, including slots 120 and 121 in a rocker body 122 and a key 123, respectively. Rocker body 122 is pinned at one of its ends to a leaf spring 124 through holes 125 and 126 and attached at its other end by a coil spring 127 to a pin 128. A perpendicularly extending pin 129, inserts into a slot 130 in key 123, acts as a key travel limit and supplies lateral key motion restraint at the front of the key. A second rocker assembly 131 requires that pins 132 and 133, “mutually parallel and non-skewed”, be assembled at one end into bearing holes 134 of key 123 and, at the other end, into hole 135 and its mate (not shown) in a bracket 136. The rocker assembly, which provides a central detent for longitudinal key motion, comes at the expense of a complexity of elements and of assembly and disassembly when pinning the rocker body both to the leaf spring at one end and the key at the other. No provision is made to damp both the z and y-axis components of unguided longitudinal key motion beyond the damping internal to the key/springs themselves. There is no means to resist substantially without play and friction lateral loads at the front of the key as longitudinal key guidance is supplied by a pin oriented perpendicularly in a slot, which is thus subject to cocking and binding. Lastly, a second rocker assembly at the rear of the key is complex to manufacture and assemble as well as a source of looseness in the keys and error in their mutual alignment.
Lastly, none of the prior art addresses how the mass of a key and the spring and player forces acting on it must be organized for player control simultaneously in the z and y axes, adding articulation to the sound.